Grinding machine

ABSTRACT

This invention relates to a grinding machine and, more particularly, to apparatus for producing a notch on the periphery of the race of an anti-friction bearing to allow the introduction of a rolling element between the races.

United States Patent Uhtenwoldt et al. 1 Sept. 5, 1972 1 GRINDING MACHINE 1,599,405 9/1926 Bugbee ..51/96 2,212,179 8/1940 Martin ..51/96 72 Inventors. Herbert R. Uhtenwold Worchester, James M. y w g y s th Mussel of Mass. 3,197,921 8/1965 Hohler et a1 ..51/165.93 X 3,269,064 8/1966 Lockwood ..51/165.9 X [73] Asslgnee: The Heald Machine Company,

Worcester Mass Primary Examiner-Lester M. Swingle [22] Filed: May 4, 1970 Attorney-Norman S. Blodgett I21 App1.No.: 34,414 [57] ABSTRACT This invention relates to a grinding machine and, more {if} 1336 .""""1'""33:1:t:::::::::::ff?f:3ii?;3l particularly,mppmwsforpmducinsanowhonthe 58 Field ofSearch.....51/96, 165.77, 165.9, 165.91, PeriPherY the race beamg 51/16592 16593 allow the introduction of a rolling element between the races. [56] References Cited 8 Claims 10 Drawing Figures UNITED STATES PATENTS 1,023,513 4/1912 Gonard ....51/96 PATENIEDSEP 5 I972 SHEET 1 OF 8 INVENTOR HERBERT R. UHTENWOLDT JAMES M. LYNCH PATENTEDsEP 5 m2 3.688.447

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PATENTEBSEP 51912 3.688.447

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GRINDING MACHINE BACKGROUND OF THE INVENTION In the manufacture of anti-friction bearings, such as ball bearings, it is common practice to provide a cylindrical notch in the bearing races in order to permit the insertion of the balls. In the past, this notch has been produced by milling the race and by hand finishing with a grinding wheel and with a brush for buffing the edges to remove burrs. This is not only time-consuming and expensive because of the manual labor used, but it does not take into consideration the fact that the distance between the bottom of the ball groove and the bottom of the notch must be at a fixed value for proper operation of the ball bearing, despite variations in the other dimensions in the race. Furthermore, this type of notching operation upsets the metallurgical quality of the metal in the race and tends to unbalance the stresses in the race. One result of this is that when the groove is subsequently finish ground, a bump or a valley may appear in the groove which, of course, tends to shorten the life of the finished bearing.

It has been suggested that these grooves could be manufactured by plunge-grinding with an abrasive wheel of suitable size. Two difficulties arise, however, in connection with an attempt to produce the notch in this manner. First of all, plunge-grinding such a deep hole is difiicult because of the rapid drop of unit grinding pressure as the wheel goes further and further into the work; the grinding becomes very slow toward the end of the notch. Secondly, the wheel diameter, of course, changes from workpiece to workpiece (because of dressing and so on) and, therefore, selecting a suitable size of wheel to produce a proper size of notch for a given ball introduction is difficult. Either the notch is too large or too small for a given ball size. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine for producing a ball-introduction notch in a bearing race by the abrasive method.

Another object of this invention is the provision of a grinding machine for producing a notch in a bearing race very rapidly and without substantial decrease of cutting rate near the finish point of the notch.

A further object of the present invention is the provision of a grinding machine for producing a notch in a bearing race in such a manner that the metallurgical properties of the face are not changed.

It is another object of the instant invention to provide a method of forming a notch in a bearing race in such a manner that subsequent finishing of the ball groove does not result in a deformed ball groove.

A still further object of the invention is the provision of a grinding machine for grinding a notch in a bearing race wherein the size of the abrasive wheel need have no particular relationship to the size of the ball to be introduced in the assembled bearing.

It is a further object of the invention to provide a grinding machine for use in producing a notch in a bearing race in which the distance from the bottom of the notch to the bottom of the groove in the radial direction remains constant despite differences in dimensions of the other surfaces of the race.

It is a still further object of the present invention to provide a grinding machine for notch-forming on the race of a ball bearing wherein the same apparatus is used irrespective of whether the race is an inner or an outer race and the notch formed is capable of receiving a ball irrespective of whether it is an inner or an outer race.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, the invention consists of a grinding machine for producing a ball-introduction notch in a bearing race, the machine having a base, having a workhead mounted on the base, having a wheelhead mounted on the base, having a spindle with an abrasive wheel rotatably mounted therein, and having means for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead. Apparatus is provided associated with the workhead for holding the race and reciprocating it through a predetermined angle about an axis parallel to and spaced from the spindle axis.

More specifically, apparatus is provided consisting of an axially-extending shaft mounted in the workhead for rocking the workpiece, and a cross-feed slide is associated with the wheelhead in addition to the conventional feed mechanism to provide for moving the wheelhead from a first position where the wheel is operative on the outer periphery of an inner bearing race to a second position at which the wheel is operative on the inner periphery of an outer bearing race.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a perspective view of a grinding machine embodying the principles of the present invention,

FIG. 2 is a plan view of the workhead portion of the grinding machine taken on the line II-II of FIG. 1,

FIG. 3 is an end view of the workhead portion,

FIG. 4 is a sectional view of the workhead taken on the line IV-IV of FIG. 2,

FIG. 5 is a sectional view of the workhead portion taken on the line V-V of FIG. 3,

FIG. 6 is an axial view of the workhead showing workholding means in place,

FIG. 7 is a sectional view of the workholding apparatus taken on the line VII-VII of FIG. 6,

FIG. 8 is a somewhat schematic view of the wheelhead and diagrammatic showing of certain workpieces illustrating the operation of the invention,

FIG. 9 is an enlarged view of a race in the process of being notched, and

FIG. 10 is a schematic view of a portion of the control for the machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, it can be seen that the grinding machine, indicated generally by the reference numeral 10, is of the type shown and described in the patent of Hohler et al. US. Pat. No. 3,197,921 which issued on Aug. 3, 1965. It is provided with a base A on which is mounted a workhead 14 and a wheelhead 13. Around the front of the base extends a splash guard B which is readily removable. Extending upwardly from the rear of the base A is a super-structure C having two arms similar to the arm D which extend forwardly from the ends of the base. Mounted between the arms is a control cabinet E. At one end of the machine is located a coolant tank F receiving coolant returned from the machine through a pipe G.

Referring now to FIG. 2, it can be seen that the workhead 14 is mounted on a swivel plate 11 which is mounted on the base'A in such a way that the angularity of the workhead assembly can be changed for producing tapered bores and the like. Extending from the workhead 14 is a shaft 12 on which is fastened a yoke 15. The yoke embraces an eccentric mechanism 16 which is mounted on a horizontal shaft 17 driven by a rotary hydraulic motor 18 whose speed can be controlled by hydraulic restrictors in the usual way.

In FIG. 3 it can be seen that the yoke 15 has two arms 19 and 21 extending around opposite sides of the eccentric mechanism 16. The lower arm 19 is provided with a pad 22 which engages the undersurface of an eccentric cam 23 forming part of the mechanism 16. The upper arm 21 is provided with an adjustable pad 24 which engages the upper side of the cam 23.

Referring now to FIG. 4, it can be seen that the workhead 14 is provided with a housing 25 carrying spaced roller bearings 26 and 27 in which the shaft 12 is carried. The shaft 12 consists of an outer tubular portion 28 and a concentric inner member 29. Both the inner and the outer members 28 and 29 are rotatable about the axis of the shaft by means of the yoke 15. However, the outer member 28 is fixed within the housing 25 against longitudinal motion, while the inner member 29 is capable of longitudinal motion by means of a piston 31 attached to the inner member 29 and slidable in a suitable bore 32 formed in the yoke 15. Suitable ports 30 and 33 are connected to the opposite ends of the bore 32 to supply pressure fluid to either side of the piston on occasion. Suitable valving and conduits are provided in the usual way to produce this motion. The other end of the shaft 12 extends from the housing 25 and is provided with workholding apparatus 34, which is described in greater detail further on and which is shown in dotted lines because of the fact that its size changes with the size of the particular workpiece to be operated on. It can be seen that the inner member 29 is provided with a head 35 which is slidable in a counterbore 36 formed in the end of the outer member 28, the outer member also being provided with a radial flange 36 extending around it.

FIG. shows the details of the eccentric mechanism 16. More specifically, it shows that the cam 23 is actually the outer race of a ball bearing whose inner race is mounted on a hub 37 which is eccentric relative to the axis of the shaft 17. The swivel plate 11 is actually attached to a workhead table (not shown) which forms part of the base A and provides for longitudinal motion of the swivel plate 11 and the wheelhead 25 and all of the mechanism associated with it.

FIG. 6 and FIG. 7 show the specific details of the workholding apparatus 34. The workpiece 38, which is shown as consisting of the inner race of a ball bearing, is supported on locating elements 39 and 41 located at the 3 oclock and 6 o'clock positions, respectively. A pressure pad 42 mounted on an arm 43 is pivotable toward and away from the workpiece to hold it in place and is engageable with the workpiece at about the 11 oclock position. As is evident in FIG. 7, the workpiece is pressed rearwardly against a platen 44 which is bolted to the head 35 on the end of the inner member 29. In the other direction, the end of the workpiece is engaged by fingers 45 and 46 which are provided with suitable nylon pads where they engage the workpiece. The locating elements 39 and 41 and the fingers 45 and 46 are all adjustably attached to a mounting plate 47 which, in turn, is bolted to the flange 36 of the outer member 28 of the shaft 12.

Referring to FIG. 8, it can be seen that the wheelhead 13 has rotatably carried in it a spindle 48 having an abrasive wheel, indicated in one position by the reference numeral 49' and in another position by the reference numeral 49' at its outer end extending toward the workhead 14. The wheelhead is mounted on a cross-slide 51 which, in turn, is mounted on the base A with a cross-feed mechanism 52 to produce the transverse motion between the abrasive wheel and the workpiece 38. The mechanism is shown as constituting a hydraulic cylinder of the type used in producing the so-called controlled force method of feeding. The cross-slide 51 consists of an upper part 53 and a lower part 54 slidable relative to one another by means of a screw 55 operable by a hand wheel 56. The relationship of the abrasive wheel and the cross-slide 51 when used with either an inner race 38 or an outer bearing race 38' is shown in this drawing.

The operation of the apparatus will now be readily understood in view of the above description. The workhead 13 is energized, the spindle 48 driven by the wheelhead motor 30 (FIG. 1). Assuming that the workpiece is the outer race 38", the workhead 14 is advanced toward the wheelhead to place the abrasive wheel 4 "in the interior of the race. The upper part 53 of the cross-slide S1 is in the position shown in FIG. 8, that is to say, POSITION No. 1. The cross-feed mechanism 52 is operated to cause the wheel to move rearwardly to the inner periphery of the race to grind therein a notch 57". Hydraulic fluid is introduced to the motor 18 which rotates the eccentric mechanism 16 and moves the yoke 15 (FIG. 3) through a slight angle up and down. This rotates the shaft 12 and causes the workpiece 38 to oscillate through the same angle. The wheel 4 is advanced into the workpiece 38", while the workpiece is being oscillated through a slight angle about the axis A-A of the shaft 12, thus generating an elongated notch. The cross-slide is placed in POSITION No. 2 when operating on an inner race 38.

Referring to FIG. 9, it can be seen that the notch 57' which is shown as formed on the outer periphery of the inner race 38, is formed with three surface portions including a central portion b-c, which is a cylindrical surface concentric with the bottom of the bearing race ball groove 58', and two end portions a-b and c-d. The latter two portions are cylindrical surfaces duplicating the cylindrical shape of the abrasive wheel 49'. Each end portion a-b and c-d is tangential to the curve b-c at the point where it joins it. The central portion 12-0, of course, lies between the bottom of the ball groove 58' and the periphery of the race in which the notch is formed. The radial distance L between the bottom of the ball groove and the said central surface portion of the notch is known as the snap distance and is of a substantial value to provide a retaining shoulder when the race is assembled into a bearing.

Referring to FIG. 10, it can be seen that a control 59 is used to maintain the snap distance the same despite variations in race CD. from piece to piece. A feeler gage 60 engages the bottom of the ball groove 58" of the outer race 38", while the outer periphery is supported by the locating element 41. The gage operates a mechanical-electrical transducer 61 whose output signal is transmitted through a contactor 62 of a relay 63 to a meter 64. The meter compares the output voltage of the transducer with the output of a transducer 65 which engages the size stop 66 associated with the cross-slide 51. When an inner race 38' is being notched, a feeler gage 67 engages the ball groove 58'. This gage stresses a transducer 68 which sends its output signal through a contactor 69 of the relay 63 (which has been energized to open the normally-closed contactor 62 and close the normally-open contactor 69) to the meter 64. The meter 64 is provided with suitable contacts in the well-known manner to terminate the grinding operation when the comparison of the transducer signals indicates that the predetermined distance between the abrasive wheel 49' or 49" and the bottom of the groove 58' or 58" has been reached.

The operation of the grinding machine is such that the distance L remains constant, irrespective of irregularities in size of the outer peripheries of the bearing races. Before the abrasive wheel 49 is used to grind the notch 57' on the outer periphery of an inner race 38', the upper portion 53 of the cross-slide is advanced to POSITION No. 2 by operating the screw 55 by means of the handwheel 56.

It can be seen that, by use of the present invention, it is possible to grind the notches on both the inner and the outer races of a ball bearing with substantially the same setting of the feed mechanism and associated control equipment. The notches will both have the same shape; that is to say, the end radii will be the same radii as the abrasive wheel, while the central portion in both cases will be concentric with the groove. This will make it easier to insert the ball into the assembled bearing and, of course, the space available for inserting the ball will be independent of the size of the abrasive wheel. [f the entire notching operation is done with the abrasive wheel, there will be substantial wear of the wheel from one workpiece to the next and, certainly, over a long series of workpieces. Nevertheless, this will not affect the opening available to insert the ball. Furthermore, because of the use of the Sizematic principle in grinding, the distance from the bottom of the notch to the groove will always be the same; in other words, the lip or shoulder defined by the snap distance will always be the same, either on inner or outer races and from one race to another.

The chief advantage of the apparatus lies in the fact, however, that grinding can take place in a much more efficient manner. With a direct plunge-grind through so much metal, the rate of feed available with a given force in the grinding machine will decrease substantially as the wheel penetrates into the workpiece and as the area of contact of the wheel and the workpiece increases. Furthermore, with the wheel operating on one part of the metal only, tremendous heat is developed and this will result not only in changing the metallurgical characteristics of the metal in the race, but also of damaging the wheel so that it becomes dull or is totally destroyed. With the present invention, the operation between the wheel and the workpiece resembles the operation with conventional internal grinding wherein the workpiece is rotated continuously at a speed substantially below the speed of the grinding wheel. In that case, the metal just ground has a substantial time to cool before it is operated on again by the grinding wheel, and this is good for the workpiece as well as the grinding wheel. In the present case, the reciprocation of the workpiece relative to the wheel has an effect on their inter-engagement similar to that experienced in conventional grinding. A spot that has just been ground has an opportunity to cool while another part of the workpiece is being operated on. This means that the wheel will last a considerably longer period of time. In an automatic machine, of course, the period in which it takes to change a wheel is inoperative time and represents non-productive use of expensive capital equipment. Metallurgically, the heat generated by continuous unrelieved grinding of a notch (as is true in plunge grinding), can cause a change in hardness of the race in the area of the notch. If the groove is subsequently finish-ground, as is usually the case, this results in either a raised part of the groove or a valley in the groove. In either case, such an interruption in the smoothness of the groove causes rapid deterioration of the balls during bearing function. The bearing, therefore, will not have a long, useful life.

It can be seen, therefore, that the present invention results in the beneficial operation of the grinding machine in the first place, and the production of a better ball bearing in the second place. The notch in the race is ground using fewer abrasive wheels and making the optimum use of the automatic grinding machine.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent rs:

We claim:

I. A grinding machine for producing a ball-introduction notch in a bearing race, comprising a. a base,

b. a workhead mounted on the base,

c. a wheelhead mounted on the base and having a spindle with an abrasive wheel rotatably mounted therein,

d. means providing for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead, and

e. apparatus associated with the workhead for holding the race and reciprocating it through a predetermined angle about an axis parallel to and spaced from the spindle axis, the said apparatus consisting of a shaft mounted in the workhead and extending at both ends from it, one end adjacent the wheelhead having a holder for locating and clamping the race against movement relative to the shaft, the other end having a laterally extending yoke attached to it, and a motor-driven eccentric element engaging the outer end of the yoke for the reciprocation thereof about the shaft axis.

2. A grinding machine as recited in claim 1, wherein the shaft consists of a tubular outer member and a concentric inner member which are movable relative to each other by a fluid pressure motor to produce clamping and unclamping of the race.

3. A grinding machine for producing a ball-introduction notch in a bearing race, comprising a. a base,

b. a workhead mounted on the base,

c. a wheelhead mounted on the base and having a spindle with an abrasive wheel rotatably mounted therein,

. means providing for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead, and

. apparatus associated with the workhead for holding the race and reciprocating it through a predetermined angle about an axis parallel to and spaced from the spindle axis, a cross-feed slide being mounted on the base and provided with a feed mechanism for producing transverse feed movement through a limited range, the slide consisting of upper and lower parts which are slidable relative to one another, and wherein the wheelhead is mounted on the upper part.

4. A grinding machine as recited in claim 3, wherein a manual rapid-adjustment mechanism is provided between the upper and lower parts, so that the wheelhead can be moved from a first position where the wheel is operative on the outer periphery of an inner bearing race to a second position at which the wheel is operative on the inner periphery of an outer bearing race.

5. A grinding machine for producing a ball-introduction notch in a peripheral surface of a bearing race having a ball groove with a bottom surface of revolution comprising:

a. a base,

b. a workhead mounted on the base and having a rotatable shaft mounted therein,

c. a wheelhead mounted on the base and having a spindle whose axis is parallel to that of the shaft and with an abrasive wheel rotatably mounted thereon,

d. means providing for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead, and

e. apparatus associated with the shaft for holding the race and reciprocating the shaft and race through a predetermined angle about an axis parallel to and spaced from the spindle axis, so that the notch is formed with three surface portions, including a central portion which is a cylindrical surface concentric with the bottom surface of revolution of the bearing race ball groove and two end portions which are cylindrical surfaces duplicating the shape of the abrasive wheel, each end portion being tangential with the central portion where it joins it.

6. A grinding machine as recited in claim 5, wherein the means for producing motion transversely of the spindle axis is operative to produce the said cnetral portion so that it lies between the bottom of the ball groove and the peripheral surface in which the notch is formed, the radial distance between the bottom surface of the ball groove and the said central portion of the notch being of a substantial value to provide a retaining shoulder when the race is assembled into a bearing.

7. A grinding machine as recited in claim 6, wherein the said radial distance is maintained at a constant predetermined value from race to race, despite variations in the dimensions of the peripheral surfaces of successive races.

8. A grinding machine as recited in claim 7, wherein a control is connected to the means for producing transverse motion to terminate such motion when a transducer operated by a feeler gage on the ball groove is in balance with a transducer engaged by a cross-slide stop. 

1. A grinding machine for producing a ball-introduction notch in a bearing race, comprising a. a base, b. a workhead mounted on the base, c. a wheelhead mounted on the base and having a spindle with an abrasive wheel rotatably mounted therein, d. means providing for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead, and e. apparatus associated with the workhead for holding the race and reciprocating it through a predetermined angle about an axis parallel to and spaced from the spindle axis, the said apparatus consisting of a shaft mounted in the workhead and extending at both ends from it, one end adjacent the wheelhead having a holder for locating and clamping the race against movement relative to the shaft, the other end having a laterally extending yoke attached to it, and a motor-driven eccentric element engaging the outer end of the yoke for the reciprocation thereof about the shaft axis.
 2. A grinding machine as recited in claim 1, wherein the shaft consists of a tubular outer member and a concentric inner member which are movable relative to each other by a fluid pressure motor to produce clamping and unclamping of the race.
 3. A grinding machine for producing a ball-introduction notch in a bearing race, comprising a. a base, b. a workhead mounted on the base, c. a wheelhead mounted on the base and having a spindle with an abrasive wheel rotatably mounted therein, d. means providing for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead, and e. apparatus associated with the workhead for holding the race and reciprocating it through a predetermined angle about an axis parallel to and spaced from the spindle axis, a cross-feed slide being mounted on the base and provided with a feed mechanism for producing transverse feed movement through a limited range, the slide consisting of upper and lower parts which are slidable relative to one another, and wherein the wheelhead is mounted on the upper part.
 4. A grinding machine as recited in claim 3, wherein a manual rapid-adjustment mechanism is provided between the upper and lower parts, so that the wheelhead can be moved from a first position where the wheel is operative on the outer periphery of an inner bearing race to a second position at which the wheel is operative on the inner periphery of an outer bearing race.
 5. A grinding machine for producing a ball-introduction notch in a peripheral surface of a bearing race having a ball groove with a bottom surface of revolution comprising: a. a base, b. a workhead mounted on the base and having a rotatable shaft mounted therein, c. a wheelhead mounted on the base and having a spindle whose axis is parallel to that of the shaft and with an abrasive wheel rotatably mounted thereon, d. means providing for producing motion longitudinally and transversely of the spindle axis between the workhead and the wheelhead, and e. apparatus associated with the shaft for holding the race and reciprocating the shaft and race through a predetermined angle about an axis parallel to and spaced from the spindle axis, so that the notch is formed with three surface portions, including a central portion which is a cylindrical surface concentric with the bottom surface of revolution of the bearing race ball groove and two end portions which are cylindrical surfaces duplicating the shape of the abrasive wheel, each end portion being tangential with the central portion where it joins it.
 6. A grinding machine as recited in claim 5, wherein the means for producing motion transversely of the spindle axis is operative to produce the said cnetral portion so that it lies between the bottom of the ball groove and the peripheral surface in which the notch is formed, the radial distance between the bottom surface of the ball groove and the said central portion of the notch being of a substantial value to provide a retaining shoulder when the race is assembled into a bearing.
 7. A grinding machine as recited in claim 6, wherein the said radial distance is maintained at a constant predetermined value from race to race, despite variations in the dimensions of the peripheral surfaces of successive races.
 8. A grinding machine as recited in claim 7, wherein a control is connected to the means for producing transverse motion to terminate such motion when a transducer operated by a feeler gage on the ball groove is in balance with a transducer engaged by a cross-slide stop. 